Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$171.32	13.429%	$194.3266	$194.33	$194.35	$194.30
Purchase #2	$50.85	12.354%	$57.132	$57.13	$57.15	$57.10
Purchase #3	$50.96	11.517%	$56.8291	$56.83	$56.85	$56.80
Purchase #4	$78.33	9.482%	$85.7573	$85.76	$85.75	$85.80
Purchase #5	$22.79	11.333%	$25.3728	$25.37	$25.35	$25.40
Purchase #6	$74.60	8.488%	$80.932	$80.93	$80.95	$80.90
Purchase #7	$36.27	13.495%	$41.1646	$41.16	$41.15	$41.20
7 purchase totals =	$485.12		$541.5144	$541.51	$541.55	$541.50